OFFSET
1,2
FORMULA
a(n) = Sum_{i=1..n} A004144(i).
MATHEMATICA
fQ[n_] := If[n > 1, First@ Union@ Mod[ First@# & /@ FactorInteger@ n, 4] != 1, True]; Accumulate@ Select[ Range@ 90, fQ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Sep 19 2010
EXTENSIONS
a(21) and a(50) corrected by Georg Fischer, Aug 29 2020
STATUS
approved